Monthly Archives: March 2016

If your car is running rough, hesitating or stalling when it is cold, you might have excessive carbon buildup on the intake valves. We usually see this happening to vehicles with 50K or more miles on them. The carbon is buildup is caused by oil seeping past the intake valve seals which is normal, and from blow by gases from the crankcase which is also normal. Shell, Chevron, Mobil and the other refiners blend gasoline with high detergent levels to clean the fuel injectors and intake valves. The detergents are formulated to inhibit and remove carbon deposits. This works on engines with port injection, but not with direct injection. So what makes the difference? Port injection engines have fuel injectors that spray gasoline right onto the intake valves. Using high detergent Top Tier gasoline in a port injection engine can clean the intake valves reducing carbon deposits. Direct injection engines spray the fuel directly into the combustion chambers. Since the fuel is no longer being sp ... read more